1. Field of the Invention
The present invention relates to a cylinder unit for mounting on a cross member and/or a table of a device or machine for the deformation of workpieces. The cylinder unit includes a cylinder block which can be mounted on the cross member and/or at the table and a pressure plate which is arranged on the surface of the cylinder block which faces away from the fastening surface, wherein a plurality of pistons each having a spherically shaped head are mounted in the cylinder block, wherein the pistons act on the pressure plate, and wherein guide bolts are arranged in the pressure plate which protrude into the cylinder block and are guided in the cylinder block.
2. Description of the Related Art
Cylinder units of the above-described type are known in the art. In these units, the spherically shaped heads of the pistons act directly on a pressure piece having a flat surface which is mounted in the pressure plate. This arrangement has the disadvantage that imprints of the pistons can be seen all the way into the workpiece.
Another disadvantage of the known cylinder units is to be seen in the fact that the guide systems of the units become easily misaligned because the cylinder block expands when it is heated by the hydraulic oil which actuates the pistons. As a result, at a temperature of 80° C., a length change of the cylinder block from one side to the other of almost 1 mm occurs.